Output resistance of a device under test (DUT) is used to determine a change in current within the DUT. As the output resistance increases, the change in current within the DUT decreases when the output voltage changed a fixed amount. A high output resistance helps to maintain consistent performance of the DUT by providing a more stable current to components within the DUT. Output resistance is measured to help determine whether the DUT will function consistently and precisely during operation.
In some approaches, output resistance is measured using a measurement tool connected to a single transistor. A voltage between a gate of the transistor and a source of the transistor, Vgs, is maintained at a constant value. Then, a voltage between a drain of the transistor and the source of the transistor, Vds, is swept through a range of voltage values. A change in current is measured as the Vds is swept through the range of voltage values, and the output resistance is calculated based on a sweep range of the Vds and the measured change in current.
In some approaches, output resistance is measured using a measurement tool connected to a single transistor connected in parallel with a current source. Similar to the single transistor approach, the Vgs is maintained at a constant value and the Vds is swept through a range of voltage values. The current source is a high magnitude fixed bias current to the transistor. The output resistance is calculated in a similar manner as the single transistor approach.